If you’ve ever towed a 5th wheel trailer, you know the drill: a large, heavy hitch taking up most of your truck bed, plenty of weight to wrestle with, and a lot of space lost for anything other than towing. For many truck owners—especially those who already use a gooseneck hitch for work—there’s a better way: the 5th wheel to gooseneck king pin box.

This specialized piece of equipment allows your 5th wheel trailer to connect directly to a gooseneck ball in your truck bed, eliminating the need for a bulky 5th wheel hitch. In this guide, we’ll dive deep into how they work, the benefits, the main types available, and which might be best for your towing needs.

What is a 5th Wheel to Gooseneck King Pin Box?

A 5th wheel to gooseneck king pin box is a replacement for your trailer’s existing king pin box. Instead of a vertical king pin that connects to 5th wheel jaws, the new box has a gooseneck coupler at its base. This coupler connects directly to the gooseneck ball in your truck bed—just like a livestock trailer or flatbed.

In essence, it converts your 5th wheel trailer into a gooseneck-style connection while still maintaining a safe, secure towing setup.

Why Switch to a Gooseneck-Style Connection?

For many owners, the motivation comes down to convenience, cost, and flexibility.

1. Free Up Truck Bed Space

A 5th wheel hitch can weigh over 200 pounds and dominates the truck bed. With a gooseneck ball, you can tow when needed and have a mostly empty bed for hauling cargo, tools, or equipment the rest of the time.

2. Save Money

If your truck already has a gooseneck hitch installed (common for farm, ranch, and construction work), there’s no need to buy a separate 5th wheel hitch. This can save hundreds—or even thousands—of dollars.

3. Reduce Weight

Gooseneck couplers weigh far less than 5th wheel hitches. Less hardware in your truck bed means less weight to lift, install, or store.

4. Easier Hookup in Some Cases

Many drivers find aligning a gooseneck ball simpler than connecting to 5th wheel jaws, especially in tight spaces or uneven terrain.

5. Keep Things Versatile

With the right setup, your truck can handle both gooseneck and 5th wheel trailers without swapping hitches or losing bed space.

Types of 5th Wheel to Gooseneck Conversion Solutions

Not all conversions are created equal. There are four main categories to consider, each with its own strengths and best-use scenarios.

1. Replacement King Pin Box (Direct Swap)

What it is:
This is a full replacement of your existing king pin box. You unbolt the old one and install a new unit that features a gooseneck coupler at the bottom.

Advantages:

• Strongest and most durable option—no long adapter shafts creating extra leverage.
• Often engineered for specific trailer frames, meaning better fit and load handling.
• Available with air-ride or shock-absorbing technology for a smoother towing experience.

Disadvantages:

• Higher initial cost compared to simple adapters.
• Installation is more involved and may require an extra set of hands or a lift.

Best For:
Frequent towing, heavy loads, and users who want maximum stability and minimal stress on the trailer frame.

2. Coupler-Style Adapter (Sleeves Over King Pin)

What it is:
A steel adapter that slides over your trailer’s existing king pin, securing with bolts or set screws, and extends downward to connect to the gooseneck ball.

Advantages:

• Low cost and simple installation—no need to remove the king pin box.
• Removable if you want to revert to a standard 5th wheel hitch later.

Disadvantages:

• Creates more leverage on the trailer frame due to its length, which can cause frame stress over time.
• Usually transfers more road shock into the trailer compared to a replacement box.

Best For:
Occasional towing, lighter trailers, and budget-conscious owners.

3. Goosebox-Style (Air Ride + OEM Approval)

What it is:
A premium air-cushioned replacement king pin box designed to connect directly to a gooseneck ball. Models like the Lippert Goosebox are approved by many RV manufacturers to preserve frame warranties.

Advantages:

• Exceptional ride comfort thanks to integrated airbags and shock absorbers.
• Often OEM-approved, so your trailer’s warranty remains intact.
• No bulky hitch in the truck bed.

Disadvantages:

• Higher cost.
• Requires periodic maintenance of the airbag system.

Best For:
Full-time RVers, heavy 5th wheels, and anyone concerned about frame stress or warranty coverage.

4. Offset Gooseneck Adapters

What it is:
An adapter or coupler with a built-in forward or rearward offset to adjust the pivot point.

Advantages:

• Improves turning clearance for short-bed trucks, reducing the risk of the trailer contacting the cab.
• Helpful in tight maneuvering situations.

Disadvantages:

• The offset increases leverage on the trailer frame.
• May not be compatible with all trailers or truck setups.

Best For:
Short-bed trucks and tight maneuvering situations, such as campgrounds or job sites.

Choosing the Right Option

Your choice will depend on a few key factors:

1. Towing Frequency – If you tow often, invest in a replacement box or Goosebox-style for comfort and frame protection.
2. Trailer Weight – Heavier rigs need stronger, better-engineered solutions.
3. Truck Bed Length – Short beds may require an offset coupler for safe turning.
4. Budget – Coupler-style adapters are cheaper but may not be as gentle on your frame.
5. Warranty Concerns – If preserving your trailer’s warranty is critical, look for OEM-approved replacements.

Applications for 5th Wheel to Gooseneck Conversions

• Farm & Ranch – Many ranch trucks already have a gooseneck ball installed for hauling livestock trailers. A 5th wheel to gooseneck conversion makes towing an RV or grain trailer just as easy.
• Construction & Trade Work – Work trucks that switch between flatbed gooseneck trailers and RVs can use one hitch for everything.
• Occasional RV Use – If your 5th wheel is used a few times a year, you can skip the heavy, expensive 5th wheel hitch.
• Maximizing Truck Bed Space – Perfect for anyone who needs their truck bed available between trips.

Potential Drawbacks to Keep in Mind

While there are many advantages, you should be aware of some potential downsides:

• Ride Harshness – Direct ball connection can be rougher than a cushioned 5th wheel hitch unless you choose an air-ride model.
• Frame Stress – Long adapter styles can place more torque on the trailer frame, which may cause long-term damage.
• Warranty Issues – Some RV manufacturers explicitly prohibit non-approved adapters. Always check before you buy.
• Clearance Requirements – Make sure your truck’s gooseneck ball placement allows proper clearance for turns and bed rails.

Final Thoughts

A 5th wheel to gooseneck king pin box can transform your towing experience—especially if you value truck bed space, already own a gooseneck hitch, or want to simplify your towing setup. Choosing the right style comes down to balancing budget, usage, trailer weight, and comfort needs.

For heavy, frequent towing, a replacement king pin box or Goosebox-style setup offers the best strength and ride comfort. For occasional use or lighter trailers, a coupler-style adapter can be a budget-friendly solution. And for short-bed trucks, an offset coupler can prevent costly cab damage while improving maneuverability.

At Hitches and Couplers, we carry a full range of 5th wheel to gooseneck king pin boxes and adapters—whether you’re looking for a rugged, frame-protecting air ride option or a simple, cost-effective coupler sleeve. With the right setup, you can tow confidently, comfortably, and without sacrificing your truck’s versatility.